Back on one of my character's first life I was doing a 12 cleric/ 7 paladin/ 1 fighter build. (I've TR'd since) and it was a sword and board character. Due to the self healing nature I could take care of most things without too much issue, it just took some time due to how slow DPS was. At least it was till Gianthold. Why Gianthold? Because it was there I started to go against a "standard party" vs. me. They have healers with unlimited SP and enough mobs to bounce about.
Given the caster's HP, I'd have to stun or trip them to stand a chance to kill it before it could toss of a Heal. Problem, they keep moving when effected, heal removes all stat damage done, should I focus on a melee, caster heals them all right back up, vorpals are useless due to deathward cast...

All in all those mob fights were always a war of attrition, with the deciding factor being only one major thing and one minor. The minor being "Who could get stuns/trips off first and longest" as those mobs can also trip. The major being, who had the larger blue bar as with damage being dealt the only thing being tossed by either side was going to be a Heal. Obviously, I lose.

The infinite blue bar to handle a semi weak AI so that we don't get a whole bunch of lag... You know, I can deal with that. It does not upset me, but fights like that just are not fun.

Much like the current thread about Hazzadil, but these aren't red name boss fights I'm talking about. But I may have an idea that could work to even it out a little.

Many experienced players realize that the mobs have one HECK of a huge healing amplification factor. (Mr. Cow has probably figured out that value long ago.) My suggestion is this:
For every curative/heal/repair/reconstruct a mob receives, their healing amplification factor goes down to the point they have zero healing amplification just like your average player.

This should make these war of attrition fights not so unfun.

Issues that I could see from this

coding: You'd want to make this adjustable per mob, so I'd load the function with a default value that can be adjusted as needed, case by case value.

Madstone Crater: We kind of need those giants we protect to have a constant healing amp that doesn't diminish.

Red/Purple named: case by case setup, but they are a boss for a reason. I'd let their healing amp not be diminished.

Undead: There is a reason I did not list inflicts in that list. Leave the undead be as they are, why? Arcane skeletons and their aura could cause this some havok if not careful.
Undead: Double check to make certain that healing amplification does not go below zero else curative/heal spells may start to deal more damage to them, or possibly less damage due to a change from nothing/positive to a negative values. (Ah sign flipping, bane of algebra and calculus.)

Player: make certain that our healing amp doesn't go down per cure.
Hireling: make certain that their healing amp doesn't go down per cure.
Summons: make certain that their healing amp doesn't go down pure cure.

Any way, just a random thought of mine. It only becomes an easy button depending on how much the diminishing factor is. Other wise, full parties would never notice a change, but smaller parties may. Or heck, it could become part of scaling.